BP_Messages_Thread::get_recipients( int $thread_id )

	public function get_recipients( $thread_id = 0 ) {
		global $wpdb;

		if ( empty( $thread_id ) ) {
			$thread_id = $this->thread_id;
		}

		$thread_id = (int) $thread_id;

		$recipients = wp_cache_get( 'thread_recipients_' . $thread_id, 'bp_messages' );
		if ( false === $recipients ) {
			$bp = buddypress();

			$recipients = array();
			$sql        = $wpdb->prepare( "SELECT * FROM {$bp->messages->table_name_recipients} WHERE thread_id = %d", $thread_id );
			$results    = $wpdb->get_results( $sql );

			foreach ( (array) $results as $recipient ) {
				$recipients[ $recipient->user_id ] = $recipient;
			}

			wp_cache_set( 'thread_recipients_' . $thread_id, $recipients, 'bp_messages' );
		}

		// Cast all items from the messages DB table as integers.
		foreach ( (array) $recipients as $key => $data ) {
			$recipients[ $key ] = (object) array_map( 'intval', (array) $data );
		}

		/**
		 * Filters the recipients of a message thread.
		 *
		 * @since BuddyPress 2.2.0
		 *
		 * @param array $recipients Array of recipient objects.
		 * @param int   $thread_id  ID of the current thread.
		 */
		return apply_filters( 'bp_messages_thread_get_recipients', $recipients, $thread_id );
	}